Add ability to pass through IDWriteFactory so sandbox can control how it's constructed

Source/web/win/WebFontRendering.cpp

Index: Source/web/win/WebFontRendering.cpp
diff --git a/Source/web/win/WebFontRendering.cpp b/Source/web/win/WebFontRendering.cpp
index a171a4127b564b35b6a4348544c99eb5432171ad..6af08c6e9befd478dc346c67aea49c79265947f3 100644
--- a/Source/web/win/WebFontRendering.cpp
+++ b/Source/web/win/WebFontRendering.cpp
@@ -16,6 +16,12 @@ void WebFontRendering::setUseDirectWrite(bool useDirectWrite)
 }
 
 // static
+void WebFontRendering::setDirectWriteFactory(IDWriteFactory* factory)
+{
+    WebCore::FontCache::setDirectWriteFactory(factory);
+}
+
+// static
 void WebFontRendering::setUseSubpixelPositioning(bool useSubpixelPositioning)
 {
     WebCore::FontCache::setUseSubpixelPositioning(useSubpixelPositioning);